Re: Star Wars mathbox math

Down to what I hope is the last issue on this boardset: what I thought was just an intensity problem (fixed with new 3904s and a 7407 in the RGB section) is in fact more interesting. The remaining failure is manifested in self-test with a dim green diagonal crosshatch & character screen (but h/v green grid is fine) and dim green outer rectangle that sometimes shifts half a screen to the right on the BIP Test (but Linear and Binary scaling are centered and bright). Ran the AVG diagnostic tests and RAM/ROM test 2, Halt test 3, long Vector test 4 pass but short Vector test 5 and Center test 6 fail (flat waveforms).

Oddly the game plays fine except for some dim green objects (western hemisphere of Death Star). I read on Jed's website that centering was hardly used, and maybe long vectors are also seldom used, so the game seems to look OK with these specific failures.

Sheet 13A shows these two signals rely on STROBE3, OP0 and OP2 along with STOP, HALT and the 12MHz clock. Clock must be good for everything else to work. HALT tests good so constituents STROBE3 and OP0 must be good. That leaves OP2 and STOP, for which there are no specific tests. Remember the short vector test passes so I'd think STOP would be ok, so maybe it's all OP2 (if that's the difference between short & long) - but I have a hard time believing the rest of the game (or indeed the state machine) would work and tests would pass if that seemingly fundamental signal wasn't working correctly.

I'd be 'glad' to try signature analysis of the AVG board but I have the HP5004 and the instructions are written for a CAT box. And surely they mean to use the main PCB in step 4 on page 18 of the Troubleshooting Guide, right?

-Douglas

On Sep 27, 2013, at 9:23 PM, Douglas Gauck <douglas@gauck.com> wrote:

> Thanks very much. Amazing how one paragraph can bring so much enlightenment.
>
> Funny I 'knew' that 'Road Accumulator' was a typo but thought the R had been subbed for an L as a bad duplicate. Was thinking 'Store' or 'Write' or 'Save' just not e for o to make 'Read'
>
> Remaining divider tests now pass after replacing the LS374 at 4L in the dividend latch. On to the AVG intensity problem!
>
> -DrG
>
>
> On Sep 26, 2013, at 6:21 PM, "Neil Ward" <Neil@wardclan.f9.co.uk> wrote:
>
>> Hi,
>>
>> From the man who designed the mathbox is an explanation of how 4000 hex represents 1.000, so 1.000 x 1.000 = 1.000
>>
>> http://www.jmargolin.com/uvmath/uvmath.htm#What Is
>>
>> I've looked at the mathbox myself, it's clever stuff:
>>
>> http://www.wardclan.f9.co.uk/Star%20Wars%20Mathbox.html
>>
>> Hope that helps.
>>
>>> PPS. Setting bit 8 of the instruction PROMs loads the accumulator, but what does it mean to set bit 9 and 'Road' the accumulator?
>>
>> It's a typo!! Should be "Read Accumulator" If you look at the schematics 'Instruction Strobe Gates' you can see that IP9 produces 'READACC' signal, which enables Accumulator outputs and writes to Math RAM.
>>
>> Good luck fixing your board!
>>
>>
>>
>> Regards,
>> Neil
>>
>>
>> ----- Original Message ----- From: "Douglas Gauck" <douglas@gauck.com>
>> To: <vectorlist@vectorlist.org>
>> Sent: Thursday, September 26, 2013 6:40 AM
>> Subject: VECTOR: Star Wars mathbox math
>>
>>
>>> Working on two SW main boards that complain about bad RAM at 5F and 5H even when replaced with known good chips. I think it's elsewhere as they also fail four of the six matrix tests (15, 16, 18 and 20), all the divider tests, and tests A, B, C and D. I would love to know how the math works as shown in the SP-225 Troubleshooting Guide for example:
>>>
>>> test 17 (passes) performs (5555-0000) x 4000 = 5555
>>>
>>> test 18 (fails) performs (0000-5555) x 0000 = 5555 if you go by the test or (0000-5555) x C000 if you go by the first diagram on page 12
>>>
>>> test 19 (passes) performs (2AAA-0000) x 4000 = 2AAA
>>>
>>> test 20 (fails) performs (0000-2AAA) x C000 = 2AAA
>>>
>>> test C performs ACC = (1B2C-0000) x 4000 + (196A-0000) x 4000 whose result should be 3496
>>>
>>> test D performs ACC = (2696-1B2C) x 4000 whose result should be 0B6A
>>>
>>> I understand binary and hex but neither is helping me understand how any of the above operations could calculate the way the guide says they do.
>>>
>>> Can anyone explain this?
>>>
>>> -Douglas
>>>
>>> PS. seems my Accumulator seems to hold onto the first value it gets, which is why 17 and 19 pass but 18 and 20 fail with 0000, A with 0001, C with 196A and D with 2696 which is interesting. Test 15 and 16 fail with 1B2C which I can't explain and B ends with 0000.
>>>
>>> PPS. Setting bit 8 of the instruction PROMs loads the accumulator, but what does it mean to set bit 9 and 'Road' the accumulator?
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>>>
>>> -----
>>> No virus found in this message.
>>> Checked by AVG - www.avg.com
>>> Version: 2013.0.3408 / Virus Database: 3222/6699 - Release Date: 09/25/13
>>
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>
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Received on Tue Oct 1 01:46:39 2013